1. Technical Field
The present invention relates to a stator of an electric motor. In particular, the present invention relates to a stator of an electric motor which has covers which cover coil ends which stick out from end faces of a stator core.
2. Description of the Related Art
In general, high output electric motors are being sought. However, to increase the output of electric motors, it is necessary to efficiently discharge the heat which is generated from the coil. For this reason, in the past, various electric motors have been proposed which efficiently discharge the heat which is generated from the coil to the outside.
Japanese Patent No. 3262716, Japanese Patent Publication No. 2008-178190, and Japanese Patent No. 3775348 disclose to insert a stator of an electric motor into a tube member and to fill an insulating resin with a high heat conductivity into the clearance between the stator and the tube member. In this case, however, the stator is increased in outside diameter by the amount of the tube member, so there is a possibility that the stator which is inserted into the tube member is not able to be placed in an existing housing.
Furthermore, Japanese Patent Publication No. 2010-68699 discloses a configuration where two covers surround the coil ends. In this case, the stator does not change in outside diameter, so the above-mentioned problem does not arise. Further, it is sufficient to prepare just covers, so the result is cheaper than with the case of using a tube member.
However, in Japanese Patent Publication No. 2010-68699, a material with a high heat conductivity is used to prepare the covers, so there is the problem that the covers more easily rise in temperature compared with the stator core.
Further, a stator is often fastened to a housing by shrink fitting. Therefore, if the stator is inserted into a heated housing etc, the covers are heated more rapidly than the stator core. As a result, sometimes the covers expand by heat and are tightly fit to the housing.
The present invention was made in consideration of such a situation and has as its object the provision of a stator of an electric motor which is provided with covers which are never tightly fit with the housing.